1. Field of the Invention
The present invention pertains generally to apparatus for press bending glass sheets, and more particularly to mobile press bending units incorporating means for centering and levelling the units as they are moved into operative position in a press bending line.
2. Description of the Prior Art
Curved or bent glass sheets are commonly employed as glazing closures for automobiles and the like. The configuration of the glazing closure, that is, the size, shape and curvature, is dictated by the opening in which the unit is to be installed and the overall design of the automotive vehicle. As will be readily apparent, with the many different designs and body styles of automotive vehicles in production at any one time, it is necessary to produce many different styles of glazing closure.
In a preferred method of producing such glazing closures in the large quantities required for efficient production, flat sheets of glass are heated to their softening temperature. The softened sheets are pressed to the desired curvature between complemental shaping surfaces, and the curved or bent sheets are then rapidly chilled in a controlled manner to a temperature below the annealing range of glass. These operations are generally carried out successively while the sheets of glass are being substantially continuously advanced by conveyor along a horizontal path including, in succession, a heating area, a bending area, and a chilling or tempering area, whereupon the residual heat in the sheet following bending can be utilized for the final heat treating or tempering operation.
The aforementioned complemental shaping surfaces are formed on opposed press members, each mounted on a supporting platen. The press members and their respective platens are normally located one above and one below the horizontal path of movement of the glass sheets to receive the sheets therebetween, and are relatively movable toward and away from each other for pressing the sheets to the desired shape. A hydraulic cylinder is generally employed for raising the lower platen and press member upwardly to engage and lift a heated glass sheet from the conveyor system, out of the horizontal path, and press it against the shaping surface of 10 the opposed or upper press member. The lower platen is then lowered to deposit the bent sheet upon the conveyor system for advancement into and through an adjacent tempering section.
As heretofore mentioned, in order to supply the needs of automobile assembly plants many differently configured glazing units are required. Moreover, with the tendency of such assembly plants to eliminate or minimize stockpiling of parts and rely upon frequent and uninterrupted delivery of the various parts, it has become increasingly important to be able to rapidly shift from production of one part to another. Conventionally, a variety of curved glazing closure parts is produced on an individual production line. Each different part, of course requires the use of different complemental shaping surfaces on the opposed press members particularly adapted to achieve the desired configuration. Initially, this was accomplished by changing the upper and lower platens and associated press members of the press apparatus on the production line. If the depth of curvature of the subsequently produced part was substantially different, it might also be necessary to change the hydraulic actuator or cylinder for raising and lowering the lower platen to one having a different length of stroke. Each time the press members are changed within the press apparatus, it is necessary to level and align them for proper operation. The entire process is time consuming and ties up the line so as to result in a significant loss in production time.
In order to reduce the time required for changing from production of one part to another, it has been proposed to incorporate the press or shaping members into a so-called portable press bending apparatus whereby the entire press apparatus can be removed from the production line and replaced by a like apparatus having the appropriate shaping members. It is thus only necessary to disconnect a minimum of drive and control members, substitute one press apparatus for another, and reconnect the drive and control members. The changeover time is thus significantly shortened and the loss in production correspondingly reduced.
While the aforementioned procedure, wherein the shaping members can conveniently be installed in the press bending apparatus away from the production line, works well and represents a vast improvement over prior art press bending techniques, it has certain limitations. Thus, even though the shaping members may be installed in the press bending apparatus and adjusted for proper operation at a location remote from the production line, the press bending apparatus must be precisely positioned as it is installed in order for the mechanism to be properly aligned and levelled relative to the production line. This again may involve an undue expenditure of time and labor which prolongs the changeover time.